getting the sum of a column exactly 12 month ago

[StefanoGrimaldi]

hey guys, 

have been trying to work something out but till now each aproach isnt giving me the correct result or its failing, 

need to determine a dax that takes as reference today dates, send me back this exact date 12 month ago and sum a column in that time period exactly, here my last attemp:

Ordenado Mes -1 = 
var actualdate = TODAY()
var fechainicial = STARTOFMONTH(DATEADD( 'Fecha Contibilización'[Date] ,-1,MONTH))
var fechafinal = MAX( ENDOFMONTH(DATEADD( 'Fecha Contibilización'[Date] ,-1,MONTH)))
var codigoarticulo = 'Query Inventario Maestro'[Codigo Articulo Corregido]
return 
CALCULATE(SUM('Reporte Ordenes'[Cantidad] ), 'Reporte Ordenes'[Codigo Articulo] =codigoarticulo, 'Reporte Ordenes'[Fecha Contabilizacion] >= fechainicial,'Reporte Ordenes'[Fecha Contabilizacion] <= fechafinal)

[StefanoGrimaldi · Accepted solution]

never mind found the soluction, 

Ordenado Mes -1 = 
var intervalo = -2
var codigoarticulo = 'Query Inventario Maestro'[Codigo Articulo Corregido]
var fechainicial =  TOPN(1, DATESINPERIOD('Reporte Ordenes'[Fecha Contabilizacion], TODAY(), intervalo ,MONTH))
var fechafinal =  ENDOFMONTH(fechainicial)
return
CALCULATE(SUM('Reporte Ordenes'[Cantidad] ), 'Reporte Ordenes'[Codigo Articulo] =codigoarticulo, 'Fecha Contibilización'[Date] >= fechainicial,'Fecha Contibilización'[Date] <= fechafinal)